Tick and Mosquito Infections Spreading Rapidly, C.D.C. Finds

Excerpted from The NY Times : (05/01/2018)

Farewell, carefree days of summer.

The number of people getting diseases transmitted by mosquito, tick and flea bites has more than tripled in the United States in recent years, federal health officials reported on Tuesday. Since 2004, at least nine such diseases have been discovered or newly introduced here.

The Centers for Disease Control and Prevention did not suggest that Americans drop plans for softball games or hammock snoozes. But officials emphasized that it’s increasingly important for everyone — especially children — to be protected from outdoor pests with bug repellent.

New tickborne diseases like Heartland virus are showing up in the continental United States, even as cases of Lyme disease and other established infections are growing. On island territories like Puerto Rico, the threat is mosquitoes carrying viruses like dengue and Zika.

Warmer weather is an important cause of the surge, according to the lead author of a study published in the C.D.C.’s Morbidity and Mortality Weekly Report.

But the author, Dr. Lyle R. Petersen, the agency’s director of vector-borne diseases, declined to link the increase to the politically fraught issue of climate change, and the report does not mention climate change or global warming. Many other factors are at work, he emphasized, including increased jet travel and a lack of vaccines.

“The numbers on some of these diseases have gone to astronomical levels,” Dr. Petersen added.

C.D.C. officials called for more support for state and local health departments. Local agencies “are our first line of defense,” said Dr. Robert Redfield, the new director at the agency, which is facing its own deep budget cuts. “We must enhance our investment in their ability to fight these diseases.”

Although state and local health departments get brief infusions of cash during health scares like the Zika epidemic in 2016, they are chronically underfunded. A recent survey of mosquito control agencies found that 84 percent needed help with such basics as surveillance and testing for resistance to pesticides, Dr. Petersen said.

Between 2004 and 2016, about 643,000 cases of 16 insect-borne illnesses were reported to the C.D.C. — 27,000 a year in 2004, rising to 96,000 by 2016. (The year 2004 was chosen as a baseline because the agency began requiring more detailed reporting then.)

The study did not delve into the reasons for the increase, but Dr. Petersen said it was probably caused by many factors, including two related to weather: ticks thriving in regions previously too cold for them, and hot spells triggering outbreaks of mosquito-borne diseases.

Other factors, he said, include expanded human travel, suburban reforestation and a dearth of new vaccines to stop outbreaks.

More jet travel from the tropics means that previously obscure viruses like dengue and Zika are moving long distances rapidly in human blood. (By contrast, malaria and yellow fever are thought to have reached the Americas on slave ships three centuries ago.)

A good example, Dr. Petersen said, was chikungunya, which causes joint pain so severe that it is called “bending-up disease.”